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Date: Thu, 05 Jun 2014 21:49:29 -0400
From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
To: Dave Jones <davej@...hat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
Linux Kernel <linux-kernel@...r.kernel.org>,
linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: ima_mmap_file returning 0 to userspace as mmap result.
On Thu, 2014-06-05 at 12:20 -0400, Dave Jones wrote:
> On Thu, Jun 05, 2014 at 11:56:58AM -0400, Dave Jones wrote:
> > On Thu, Jun 05, 2014 at 06:40:36AM +0200, Michael Kerrisk (man-pages) wrote:
> > > On 06/05/2014 01:31 AM, Dave Jones wrote:
> > > > I just noticed that trinity was freaking out in places when mmap was
> > > > returning zero. This surprised me, because I had the mmap_min_addr
> > > > sysctl set to 64k, so it wasn't a MAP_FIXED mapping that did it.
> > > >
> > > > There's no mention of this return value in the man page, so I dug
> > > > into the kernel code, and it appears that we do..
> > > >
> > > > sys_mmap
> > > > vm_mmap_pgoff
> > > > security_mmap_file
> > > > ima_file_mmap <- returns 0 if not PROT_EXEC
> > > >
> > > > and then the 0 gets propagated up as a retval all the way to userspace.
> >
> > I just realised that this affects even kernels with CONFIG_IMA unset,
> > because there we just do 'return 0' unconditionally.
> >
> > Also, it appears that kernels with CONFIG_SECURITY unset will also
> > return a zero for the same reason.
>
> Hang on, I was misreading that whole security_mmap_file ret handling code.
> There's something else at work here. I'll dig and get a reproducer.
According to security.h, it should return 0 if permission is granted.
If IMA is not enabled, it should also return 0. What exactly is the
problem?
thanks,
Mimi
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